geology and ore deposition

The Boundary Cone, a volcanic plug, may be seen in the 9.-View showing the structure of the Gold Road vein with nearly 10.-The hanging wall portion of the Gold Dust vein, showing 11.-The

Hager, Dorsey, Practical Oil Geology, MeGraw-Hill Book Company,

370 7th Ave., New York City-$3.00

Lilley, E R., The Geology of Petroleum and Natural Gas, D VanNostrand Co., Ine., 8 Warren St., New York City-$6.00.Panyiti, L S., Prospeeting for Oil and Gas, John Willey and Sons,Ine., 440 4th Ave., New York City-$3.25

Van Wiebe, ""V A., Oil Fields of the United States, MeGraw-Hill BookCompany, 370 7th Ave., New York City-$6.00

Warner, C A., Field Mapping for the Oil Geologist, John Wiley &Sons, Ine., 440 4th Ave., New York City ;-$2.50

Zeigler, Vietor, Popular Oil Geology, John Wiley & Sons, Inc., 440 4thAve., New York City-$2.50

50 ARIZONA BUREAU OF MINES

Comparison with Districts having Similar Types of Ore _ 94 Mines of the Oatman District _ _ _._,_ _._ 101 Mines of the Katherine District _ _ _ _.115 Future Possibilities in the Oatman and Katherine Districts 124

I.-Index of Map of the Oatman and Katherine Districts 9

2.-Chart showing the relation between tons of ore mined and the

value per ton for the years 1908-1928 inclusive 17

S.-Topography of the higher slopes of the Black Mountains to the

4.-Topographic relief in the foot-hill belt to the west of Oatman 19

5.-The detrital slopes to the west of the Katherine Mine 20

6.-General view of the town of Oatman from the south The

white area in the lower central part is the tailing pile of the

7.-The Elephant's Tooth, a rhyolitic plug to the east of Oatman 47

8.-A general view of the southwestern part of the Oatman

Dis-trict The Boundary Cone, a volcanic plug, may be seen in the

9.-View showing the structure of the Gold Road vein with nearly

10.-The hanging wall portion of the Gold Dust vein, showing

11.-The first stage of quartz deposition The dark band is the

12,-Plat.y quartz as a pseudomorphic replacement of calcite

lS.-Quartz of the second stage of deposition, showing a

14.-Banded quartz of the third stage of deposition A variety

15.-Quartz of the fourth stage of deposition The platy structure

16.-Dark greenish quartz of the fifth stage of deposition The

17.-A specimen of the fifth stage of deposition This quartz is of

a dark greenish color The white band is adularia 71

18.-Diagrammatic section showing decrease in the value of the

19.-Diagrammatic section showing more extensive erosion of ore

shoots in the western part of the Oatman District 81

20.-0utcrop of the Gold Road vein in the Oatman District 86

21-0utcrop of the Black Dyke vein il) the Katherine District 86

22.-A general view of the Tom Reed plant at Oatman 101

2S.-View across the tailing pond to the No.2 shaft of the United

24.-A view up Gold Road Gulch Remains of the old mill in the

25.-General view of the Moss Mine The dark outcrop of the vein

26.-A map of the veins and faults at the Moss Mine 114

27.-Vertical section through the Katherine Mine Based on maps

28.-A general view of the plant of the Katherine Mine 118

29.-View of the Frisco Mine showing the veins at the contact of

SO.-Vertical section through the Frisco vein The vein occurs at

the contact of rhyolite and granite Not drawn to scale : 12:2

TABLES

Page

Table H.-Gold and Silver Production of the San Francisco District,

Table HI.-Summary of the Characteristic Features of the Various

Ta:ble IV.-Production and Metal Contents of OTe from the San

Francis-co District, Arizona 1908 to 1928, inclusive 77

Page

Plate I.-Geologic map of the Oatman District, Opp p _._ _ :_ 20

Plate II.-Geologic map of the Katherine District _ _ _ 21

Plate IlL-Structure sections of the Oatman District _ c • _ 51

Plate IV.-Location of ore shoots on the Tom Reed vein and the Gold

PREFACEThe Arizona Bureau of Mines considers itself fortunate in be-ing privileged at this time to publish this report on the "Geologyand Ore Deposits of the Oatman and Katherine Districts." Amere descriptive paper would doubtless prove valuable in attract-ing attention to these districts, but Doctor Lausen has writtensomething much more significant While it has long been knownthat some of the veins could be mined profitably, while otherscould not, the reason for the differences in mineralization hasbeen a mystery, and, as a result, much money has been wasted inexploring veins which it is now known do not contain the type ofvein filling that is associated with good gold values in these dis-tricts Doctor Lausen has, apparently, solved the problem, andhas succeeded in discovering certain facts as regards the veinfillings that should prove extremely valuable when applied in sub-sequent operations Recognition of the fact that only fourth orfifth stage quartz and associated minerals, as described herein,contain enough gold to be minable at a profit is an achievement

of great potential value

It is recognized that the descriptions of mines and prospectsare not in every case as complete as might be desirable, and thatsome meritorious properties may not even be mentioned, but thetime available for the preparation of this paper did not suffice togather the data required for a really detailed report Because

of the existing keen interest in gold properties, it was thoughtbest not to delay publication until additional information could

be collected and compiled

Suites of specimens representative of all the different stages

of vein fillings described herein are possessed by the Bureau andmay be examined by anyone Furthermore, the geologists of theBureau will be glad to assist prospectors or miners by determin-ing to which stages of vein filling samples submitted for examin-ation belong, if iUs possible to do so June 1, 1931

G M BUTLER, Dil'ect01'.

GEOLOGY AND ORE DEPOSITS

OF THE

By CARL LAUSEN

INTRODUCTION AND ACKNOWLEDGEMENTS

The Oatman and Katherine districts have produced more than

thirty million dollars worth of gold and silver yet no complete

re-port on the geology and ore occurrence of this interesting region

is available though numerous short papers on various phases of

its geology or the mining operations conducted there have been

published from time to time A thorough study of the Oatman

District was made by Dr F L Ransome and a preliminary

re-port2 based on that study was issued by the United States

Geo-logical Survey in 1923 The detailed descriptions of the rocks

and the excellent map of the district accompanying this report

have been of great value to the operators in this district As Dr

Ransome has left the Geological Survey, it is hardly likely that

a complete report will be written by him and published Among

the earlier accounts of the district, that by Mr F C Schrader3

is, by far, the most complete Although Schrader's report is

based upon a reconnaissance examination of the district, as

stated in the introduction, it served a usefui purpose until

super-seded by Ransome's more detailed studies Schrader's work, which

preceded Ransome's by fifteen years, was done at a time when a

farge number of the properties were operating The bulletin,

therefore, contains much information on the character of the

vein fillings and the grade: of· the' ore mined Both Ransome's

and Schrader's bulletins have been drawn on freely for

infor-1 Submitted as a thesis in partial fulfillment of the requirements for

the degree of Doct01.· of Philosophy at the University of Arizona, May, 1931.

2 Ransome, F L., Geolo:gry of the Oatman Gold District, Arizona: U S.

Geological Survey Bull 743, 1923.

3 Schrader, F C., Mineral Deposits of the Cerbat Range, Black

Moun-tains, and Grand Wash [Cliffs, Mohave County, Arizona: U S GeoL Survey

Bull 397,,1909.

GEOGRAPHIC FEATURES

LOCATION AND ACCESSIBILITY

Local names were, at one time applied to parts of the minin~

district of the Black Mountains, such as Gold Road District,

Vivian District, Union Pass District, and others In reality, these

localities comprise what is officially the San Francisco Mining

District A local concentration of veins occurs around Oatman

and another from Union Pass westward, while the intervening

country, particularly north of the Moss property, and south of

Thumb Butte, although not entirely devoid of veins, is more

sparsely mineralized On this basis, an arbitrary subdivision

into the Oatman District and the Katherine District is made in

this report for the sake of clearness, as those acquainted with

the region are more familiar with the particular area under

I

/~'!: Thumb Buffe

I

J,

'X':MOSS MINE

' ~ b,NufIMf.

THE OATMAN AND KATHERINE DISTRICTS

Fig I.-Index map of the Oatman and Katherine Districts.

cussion when the terms Oatman District or Katherine Districtare used rather than when the broader term, San Francisco Min-ingDistrict, is employed

All the important veins in both districts occur on the westslopes of the Black Mountains, in the western part of MohaveCounty Highways connecting the mining camps with Kingman,

ARIZONA BUREAU OF MINES

8

mation on,the underground workings of properties now

inaccessi-ble Frequent short notices in the technical press deal chiefly

with mining or metallurgical problems, and rarely make more

than a brief mention of the geology, and then usually treat of the

geology of some particular mine rather than of the dish-ict,as a

whole

The writer, while a member of the staff of the Arizona Bureau

of Mines, visited the region at various times whiTe the geologic

map of the state was in preparation Later, he examined the

Oatman and Katherine districts for the United Verde Copper

Company Since then, additional trips have been made, chiefly

in connection with special problems on general geology, faulting,

and ore deposition

A laboratory study of ores and associated country rocks has

yielded results, some of which are not only of scientific interest,

but also of considerable economic importance

The operators in botb, districts have given freely of the data

accumulated during the years of operation in the,district Among

them, may be mentioned in particular, Messrs Victor Light and

Chas Waters of the Tom Reed Gold Mining Company, Mr J W

Bradley of the United Eastern, and Mr R H Dimmick of the

Katherine Mine Numerous others in both districts have been

obliging enough to take the writer to their properties

Mr J B Tenney, of the Arizona Bureau of Mines, kindly

com-piled the information on production records

To the staff of the Department of Geology of the University

of Arizona, the writer is under obligations for aid in the

labora-tory investigation of ores and for suggestions during the prepa-·

tion of this report

THE OATMAN AND KATHERINE DISTRICTS ARIZONA BUREAU ()FMINES

CLIMATE

The region is characterized by an arid climate, with high

tem-peratures prevailing during the summer months, and a

rela-tive low humidity Cloudy days are rare and even in: the

win-ter a sunny day may be quite warm Extremes of temperature are

shown in Table 14for Ft Mohave, about fourteen miles to the west

of Oatman, and for Kingman 29 miles to the east The extremes

of temperature do not picture accurately the climatic conditions,

and for that reason the mean monthly temperatures are also

giv-en The average monthly rainfalls at Ft Mohave and Kingman

are also given No records are available for Oatman, but the

temperature can be expected to be somewhat lower than at Ft

Mohave and higher than at Kingman A diurnal change in

tem-perature of 50° to 60°F has frequently been recorded, and a

the county seat, traverse the mountains through low passes U; S

Highway 66 in northern Arizona crosses the Black Mountains

at Sitgreaves Pass; the distance from Kingman to Oatman by

this road is 29 mnes The road from Kingman to the Katherine

Mine crosses the range at Union Pass; the distance between

the two points iSI approximately 35 miles Still farther north,

several other roads cross these mountains The position of these

camps relative to Kingman is shown on the index map, Fig 1

Kingman is the nearest shipping point on the Atchison,

To-peka, and Santa Fe Railway, and power for the Oatman

Dis-trict is generated there To the southwest of Oatman is Topock,

a station at the bridge across the Colorado River, and about

eighteen miles to the northwest of Topock is Needles, a division

point on the railway

In the early days of Oatman, a narrow-gauge railroad,extended

from the Vivian and Leland mines to Fort Mohave on the

Colo-rado River At that time, a ferry was operating at Ft Mohave,

and supplies for the mines were' brought in from Needles,

Cali-fornia

Numerous short roads lead from the main highways to the

individual groups of claims, but many of them are now

impass-able One of these roads leads off of the main highway about

midway between Oatman and the Gold Road Mine and follows

Silver Creek to the mines in the northwestern pa.rt of the

Oat-man District A branch from the Silver Creek Road turns north

and connects with the Union Pass Road just north of Thumb

Butte

4 Smith, H V., The Climate of Arizona: Bull No 130, Agricultural

Experiment Station, University of Arizona, 1930.

10

~ .nzn

marked drop of temperature usually occurs where a bright, sunny

day is followed by a clear, star-lit night

The elevation above sea level is an important factor in deter

mining climatic conditions The elevation at Ft Mohave is 604

feet above sea level, at Kingman it is 3,326, while at Oatman it

is 2,700 feet

Rainfall is also dependent, in a measure, on elevation Table I

shows the average annual rainfall at Ft Mohave to be 5.21

inches, while at Kingman it is 11.50 inches At Oatman, it is

between these two figures In Arizona, the rainfall is seasonal;

the heaviest showers occur during the summer months,

particu-larly during July, August, and September During these months,

the showers are nearly always accompanied by violent electric

storms which are of rel'atively short duration, but, during these

brief storms, a large volume of water may fall For the

remain-ing months, the rainfall is chiefly concentrated in December to

March, inclusive Gentle showers are then the rule,~but heavy

showers may occur

The rainfall record at Ft Mohave, shown in Table I, represents

an average of 44 years, while the temperature record is based

on 13 years of observation The figures given for Kingman, both

temperature and rainfall, are based on a 25-year record, and have

been compiled from official government som:ees

HISTORY AND PRODUCTION

Much of the early history of discovery and mining in these

districts is obscure According to Ransome's bulletino, Gen J H

Carleton and the 5th California Volunteers were stationed at

Ft Mohave in 1862 As some of the soldiers were experienced

gold miners from California, they prospected the surrounding'

country when not on military duty Some of these

soldier-pros-pectors probably discovered the Hardy vein and established the

settlement on Silver Creek Fragments of old stone walls' are still

standing as a monument to these pioneers

About 1863, John Moss located the Moss vein Some reports

state that he was led to this deposit by friendly Indians who

showed him specimens of quartz which contained free gold The

outcrop of this vein is said to have contained considerable free

gold, particularly at one place About this time, the Mossback

vein about two miles to the east was located Considering the

prominence of some of the veins as features of the landscape,

particularly the silicified portions of the Tom Reed and Gold Road

veins, it is surprising that ore shoots in them were not

discov-ered earlier

13

THE OATMAN AND KATHERINE DISTRICTS

GOp cit p 154.

Very little reliable information is available concerning

activi-in the district duractivi-ing the seventies, eighties, and early nactivi-ine-Apparently, work continued on the veins in the vi~initySilver Creek, and, as interest waned, the prospectors mIgrat-

nine-ed to areas of greater promise It is possible that the discover~

of rich silver-gold ores in the Cel'bat Range to the north ofKingman, in the early seventies, drew the attention of prospec-nors away from the region of Silver Creek Such are as wasmined along Silver Creek was hauled to Hardyville on the Colo-rado River for treatment The reason for so doing was the gen-eral absence of water in this region, although a small seep OCCUI'S

near the old settlement on Silver Creek where bedrock is posed at the surface That some of the ores, perhaps the rIcherones, were treated near the settlement, is suggested by the pres-ence of an old arrastre cut out of solid stone

ex-From such information as' is available, it seems probable thatthe earliest locations in the Katherine District, the Sheeptrailand Boulevard mines, were made in the early eighties The orefrom these two mines was hauled to the Colorado River for treat-ment in the Pyramid mill A teamster hauling this ore to theriver had passed a small granite knob about midway between themines and the river many times Examining this outcrop, henoticed numerous stringers of quartz traversing the granite, and,

on panning a sample, he obtained a string of colors .This ~ed

to the discovery and locations of the present Katherme Mmeabout 1900 or 1901

Prospectors from the settlement on Silver Creek, searching thehills to the southwest, located a number of veins There, theLeland and the Vivian were located prior to the year 1891, thePioneer about 1896

A discovery which led to a more thorough prospecting anddevelopment of the region was the finding of fre: gold in th.e out-crop of what was later termed the Gold Road vem Accordmg toSchraderG, the locations were made by Joe Jeneres in 19~2.

J eneres was grubstaked by Henry Lavin of Kingman The covery was said to have been accidental A sample taken fromthe outcrop is said to have carried forty ounces in gold pel' ton

dIS-The announcement of this discovery led to an influx of prospectorsand many claims were located

The Tom Reed vein was located about 1900 and changed hands

a number of times before the present company took over theholdings in 1908 In 1901, the Gold Road Company put down

ARIZONA BUREAU OFlVIlNES

12

THE OATMAN AND KATHERINE DISTRICTS

value of the ore decreased or production dropped off ; t '

wane ,an a penod d ' d of stagnation set in Many of th ' n e1 est

ven-UI es aI ed to find ore and, unable to raise additional capital tcarryon, the claims were often abandoned The cycle is the~

dis-covenes are made

Foll?w,ing ~he discovery of the United Eastern ore body in1,915, ,It IS SaId that fully 200 properties were operating at onetIme m the Oa~man District ?uring 1916, eighty differentshafts were bemg sunk at varIOUS properties Of this largenumber" only a few encountered new ore bodies, usually near thesurface m the zone of enrichment where higher values could bexpected Such enriched ores seldom continued in depth mol':than a few hundred feet below the point of discovery

The ore at the United Eastern was first encountered at adep,th of 3~0 feet below the surface This discovery led to thebelIef that It was necessary to attain this depth before ore could

be e~pected. The number of shafts eventually sunk to depthsrangmg from 300 to 600 feet thoroughly exploded this fallacy., A ,record of the production from the Oatman and KatherinedIStncts has, been cOl?piled by Mr J B Tenney of the ArizonaBureau of~mesand IS given in Table II As shown in this tablethe productI?n from ,the various mines prior to 1907 is more 01:les~ uncert~m, an? IS ba~ed on such records as are available

Th~s table I~ also mterestmg because it shows the years during,,:hlCf the dIfferent large mines were the main producers of thedIStrIct

Production prior to 1908 is given as $2,500,000 This figure

R~ad,Mm~ for the penod of 1904 to 1907 inclusive; and the Mossvem IS, saId t,o have produced $250,000 from the original discov-ery TheeS~Imate does not cover the production from the Hardy

productIOn f.r0m the Katherine District or the various propertiesaround and mcluding the Vivian

Table II s~ows that the main period of production from theGold Road Iy.Ime was from 1904 to 1915, inclusive This mine wasshut down In 1918, reopened in 1922, and again closed in 1924.The Tom Reed Company produced from 1908 to 1921, and from

1922 to May, 1924, g?ld production was entirely by lesseeswhose ore was treated m the Tom Reed mill Production by thecompany, beg,an agai~ from the Black Eagle shaft in 1927 Thetotal productIOn credIted to this company includes also in thelater years, a small production from outlying propertie; Pro-

ARIZONA BUREAU OF MINES

two shafts to a depth of 100 feet and discovered some ore in each

shaft

At the time of Schrader's examination of the district, in 1906

and 1907, a numbet of companies were operating; some were

producing gold, others were developing their holdings

Additional claims were located from time to time after the

earlier discoveries among them the Grey Eagle and Bald Eagle,

in 1904, that wer~ destined to play an important part in a

law-suit at a later date These claims are to the southeast of the·

Ben Harrison shaft of the Tom Reed Company, and are now a

part of the holdings of that company,

In March, 1913, McIver and Long obtained an option on ground

which later formed the main holdings of the United Eastern,

According to some statements the U E, vein was first

recog-nized in the Tom Reed Mine Miners, working in the Tom Reed

Mine noticed that the vein split into two branches, the main

which also contained some vein filling, had a more nearly

south trend, Development work continued on the main or

north-west branch, but, at the time, the branch was not developed., In

1915 the United Eastern Gold Mining Company was orgamzed,

and the shaft started by McIver and Long was continued by the

company By the end of 1916, a considerable tonnage of ore with

a value of about $22 per ton had been blocked out, and a 200-ton

mill was completed

The next important discovery was the finding of ore on the

Big Jim claim to the east of the Tom Reed vein This claim was

later (1917) acquired by the United Eastern Company, and led to

litigation with the Tom Reed Company

In 1917 the Telluride vein was discovered, and, although the>

ore body ~asrelatively small, it was rather rich This discovery

was the latest important one made in the Oatman District ~l­

though some rich ore was found in a winze at the Sunnyside vent

below the 500-foot level in 1927 The ore shoot was

compara-tively small and soon play~dout in depth ,

Both the Oatman and Katherine districts, like so many of the

bonanza gold districts of the west, have had a checkered

his-tory The spectacular character of sO,me of the rich ore~nd t~e

possibility of fortunes being made qUIckly appeal to the

Imagm-ative mind Each new discovery led to a period of excitement

during which many new claims were located, or old ones

re-located; additional capital was brought in to try! out new v~n­

tures' activity increased by leaps and bounds and prosperIty

14

TABLE n.-GOLD AND SILVER PRODUCTION OF THE SAN FRANCISCO DISTRICT, ARIZONA

I Bullion Tons I Bullion Total Tonsl Total Gold Total SilverTota~Value

""'l

~

Cl

""'l

f-'

~

THE OATMAN AND KATHERINE DISTRICTS 19

Fig 4.-Topographic relief in the foot-hill belt to the west of Oatman.

tween the massive flows are softer tufaceous members that inplaces weather to form more gentle slopes At several places,the continuity of these nearly vertical cliffs is interrupted byfaults Side canyons, although of a steep gradient, make thehigher region accessible Cottonwood Creek, which heads in thisportion of the range, in its upper reaches, has formed a canyon

of wild scenic beauty This rugged type of topography continues

in the higher portions of the range northward for many miles,even beyond Union Pass

moun-tains proper merges imperceptiblYI into the foothill belt; in

oth-er places, the change is more abrupt Flanking the range on thewest side, a region of lower elevations and gentler sropes formsthe foothill belt It~ width is quite variable, ranging from twomiles to six miles The relief consists of a more mature topog-raphy intricately dissected by stream erosion 'Dhe hills rarelyrise more than a few, hundred feet above the stream bed Thehill tops are well rounded and the slopes are usually gentle Hereand there, however, particularly in areas in which the Esperanzatrachyte is exposed, a more rugged topography exists This con-dition is particularly notable in areas around the BoundaryCone

Intrusive plugs of rhyolite form prominent features of thelandscape Two such plugs occur in the Oatman District Theyare somewhat lighter in color than the lavas which they invade,and Boundary Cone, in the southwestern part of the district, isthe most prominent This conspicuous feature of; the landscape

is visible for long distances, especially from the west T'hisplug rises 1,400 feet above Esperanza Gulch in a horizontal dis-

ARIZONA BUREAU OF MINES

18

PHYSIOGRAPHY

In both the Oatman and Katherine districts, aU the veins so

far located occur on the west slope of the Black Mountains or in

the lower country to the west, between the range and the

Colo-rado River The mineral-bearing area may be subdivided on the

basis of topographic relief into three belts or units with a

north-south trend These are, 1st, the rugged uplands, 2nd, the

foot-hill belt, and, 3rd, the detrital slopes

Rugged Uplands: At Sitgreaves Pass, where the main

high-way between Oatman and Kingman crosses the mountains, the

elevation is nearly 3,600 feet above sea level South of this pass,

the mountains, as viewed from a distance, present a mesa-like

appearance due to what appears to be nearly flat lava flows In

reality, these flows are deeply dissected by streams which flow to

the east or south Antelope Creek, within a mile of its head at

the crest of the range, just east of the town of Oatman, has cut

a canyon into these lavas, which is nearly a thousand feet deep

Basalt flows are present less than two miles south of Antelope

Canyon and there the mesa-like relief is even more apparent The

drainage is to the south through Warm Springs Canyon, This

particular part of the range is frequently referred to as the Ute

Mountains

North.of Sitgreaves Pass, the topography is much more

rug-ged In this area, Nutt Mountain, with an elevation of 5,065

feet above sea level, forms the highest point in the Black

Moun-tains Surrounding Nutt Mountain on all sides, the relief forms

a terraced topography of cliff and slope In some places, the

more massive flows form cliffs, from 300 to 500 feet high

Be-Fig B.-Topography of the higher slopes of the Black Mountains to the

east of Oatman, Arizona.

Fig 5.-The detrital slopes to the west of the Katherine Mine.

ARIZONA BUREAU OF NUNES

tance of somewhat less than a half mile The Elephant's Tooth,east of the town of Oatman, another plug of rhyolite porphyry,

is the erosional remnant of a dike with a local increase in width.Intrusive porphyry forms a rugged area to the northwest ofOatman The highest point, Mt Hardy, attains an elevation of3,231 feet above sea level and a thousand feet above Silver Creek,immediately to the north The rock is traversed by a large num-ber of joint planes along which erosion has cut numerous ruggedcrags

In the southeastern part of the Katherine District is ThumbButte, a prominent feature of that region The rock from whichthis butte is carved is a thoroughly consolidated volcanic ag-glomerate Erosion has cut the upper part of this agglomerateinto a series of sharp pinnacles and crags

slopes which extend from the foothill belt westward to the rado River The general uniformity of this slope is its moststriking feature In its upper reaches, the surface slopes at therate of 200 feet to the mile, but, nearer to the banks of the river,the slope has decreased to somewhat less t'han 100 feet to the_mile Long, dry washes, broad and shallow, drain the region.These washes rarely carry water except after heavy storms, but,the streams carry large quantities of sand, gravel,' and evenlarge boulders when in flood At present, the streams have cuttheir beds to depths which rarely exceed 50 feet below the oldsurface

Colo-The down-cutting of the streams has developed a series of races Particularly good examples occur on Silver Creek near the

ter-20

GENERAL GEOLOGY

Oatman Amalgamated Mine Only a few isolated remnants

re-main, and the shifting· of Silver Creek from side to side has cut

deeply into the few remaining remnants

23

THE OATMAN AND KATHERINE DISTRICTS

There is a small exposure of these older rocks near the ock shaft, in the southwestern part of the Oatman District.his brownish, somewhat schistose rock may be a partly recrys-allized sediment Itis rather fine-grained in texture with abun-dant mica flakes on parting planes In this vicinity, also, is an

Mur-~xposure of fine-grained diorite The rock is somewhat altered,

but appears to consist essentially of feldspar and a sian mineral, perhaps hornblende, together with a small amount

ferromagne-of accessory magnetite

The older rocks occur a short distance to the west of :B'ortunaHill, in the western part of the Oatman District, where a small ex-posure of biotite gneiss is cut by granite The granite is uni-form in texture, the large feldspars rarely exceeding two-tenths

of an inch in length The minerals are potash feldspars, bothicrocline and orthoclase, some acid plagioclase,and quartz.erromagnesian minerals are rare, but the form of some iron-tained patches suggests derivation from biotite A little mag-netite may also be seen in the hand specimen The rock iscream-colored on fresh fracture and weathers pale brownish It

is somewhat altered and seamed with veinlets of caIcite, and thefeldspars are kaolinized In texture and mineral composition,this granite closely resembles the rock cut in deep diamond drill-ing at the United Eastern Mine, but the granite from the minecontains a small amount of chlorite

The prevailing rock in the Katherine District is a

coarse-grain-ed granite Ona weathered surface, it is brownish due to the de.composition of the ferromagnesian constituents Surface ex-posuresare highly altered and crumbly Even in the deep~r

workings ofjthemines, it is practically impossible to obtain mens that do not show intense alteration Specimens from theine workings have a greenish-gray color due to abundant chlo-ite Intense shearing has crushed the large crystals of bothquartz and feldspar, and has produced a gneissic structure Therock is rather coarse-grained and somewhat porphyritic in tex-ture, with large phenocrysts of microcline rather common 'Thesephenocrysts are rounded in outline and measure up to two inches

speCl-in diameter The matrix of the rock in which the large crysts are set consists of) quartz and feldspar grains rar.ely le~sthan one-quarter inch and frequently over one-half mch mdiameter The quartz is of an opalescent, bluish color and trans-lucent rather than transparent The feldspars are nearly allmore or less kaolinized Between the quartz and feldspar grains

pheno-is abundant chlorite to which most of the dark color of the rock pheno-isdue Associated with this chlorite are grains of pyrite, and it

ARIZONA BUREAU OF MINES

22

PRE-CAMBRIAN FORMATIONS

The underlying rocK on which the Tertiary lavas rest is

ex-posed in several small areas in the western part of the Oatman

District Deep diamond drilling at the United Eastern Mine

shows that the andesites at that mine rest directly on the

highly sheared granite A small exposure of sheared granite

present on the east side of the range opposite Oatman, only a

short distance south of the highway

Granite is the prevailing type of rock in the Katherine

trict A prominent ridge, which extends eastward to the base of

the range, just south of the Katherine Mine, is composed of

granite with local, small patches of lavas About a mile south

of Union Pass, a beltofthis granite crosses the crest of the range

and extends eastward an unknown distance Shafts sunk through

the surface gravel at various properties near the Katherine Mine

have penetrated the granite in depth The intervening country

on the west side of the Black Mountains, between the Oatman

and Katherine districts, also contains isolated exposures of the

older rocks

Although the formation as a whole is essentially granitic, in

reality it is a complex of various old rocks, such as schist and

gneisses, highly sheared and altered At least two different

granitic intrusions occur in these districts with marked

differ-ences in mineral composition and texture Both, however, are

younger than and intrude the schist-gneiss complex

There is no positive proof in either the Oatman or Katherine

districts that this complex is pre-Cambrian in age, but its highly

sheared and altered condition suggests that it belongs in the

old-er divisions of geologic history Not far to the

north-east-ward, in the lower slopes of the Grand Wash Cliffs, are

exten-sive exposures of a coarse-grained, highly sheared granite,

re-markably similar in appearance to the granite in the Katherine

District, which is overlain unconformably by Paleozoic

sedimen-tary rocks the oldest member of which is a sandstone of Middle

Cambrian age The older rocks in both the Oatman and

Kath-erine districts are therefore assigned to the pre-Cambrian

divi-sion of geologic time

The order of crystallization of the constituents of this rockappear to be zircon, apatite, hornblende, magnetite, pyrite, plagi-oclase, Ol:thoclase, microcline, and quartz.

The texture may be described as allotriomorphic with a dency towards idiomorphism for the grains of plagioclase feld-spar

ten-The rock may be described as a hornblende-microcline granite

A striking feature of the rock is the entire absence of micaceousminerals such as biotite or muscovite

Dikes of pegmatite and pegmatitic quartz are quite common inthe granite of the Katherine District They do not present anyfeatures of special interest

Near the road leading west from Union Pass is a small posure of rock which is weathering to an olive drab soil Decom-position is so far advanced that it is impossible to get a speci-

ex-en for accurate determination It appears to have been diorite

or gabbro Certain dark dikes cutting the granite are hornblendediorite porphyry and may be related to this diorite or gabbro in-trusion

THE OATMAN AND KATHERINE DISTRICTS 25

MURDOCK BRECCIA

Near the Murdock Mine, in the southwestern part of the

Oat-an District, is a detrital deposit which is here named the ock breccia Itconsists very largely of granitic detritus togeth- with angular fragments and boulders of granite, gneiss, SChist,ein quartz, and some dark-,rocks, perhaps diorite The matrix inhich these more resistant rocks are set is composed of angularrains of quartz and feldspar derived from the disintegration ofposures of granite More or less red mud occurring in theatrix was probably formed from the decomposition of the feld-aI'

Mur-The material at this locality shows little or no sorting, and aixture of large and small boulders is a common characteristic

om a distance, however, a rude stratification is discernible

d the deposit near the Murdock Mine appears to dip to the westabout 25°

About two miles west of the Leland' Mine are extensive ()sures of this formation The material of which it is composedvery much the same as that near the Murdock Mine, but thelor, particularly in the upper portions of the deposit, is green-

ex-h ratex-her tex-han brown A closer examination shows more net bedding The greenish portion appears to consist partlyvolcanic ash, and may represent material derived from the first

dis-of volcanic activity

ARIZONA BUREAU OF MINES

is possible that the solutions that ~eposited the ~yrite also

changed the original ferrogamnesian mmerals to chlorIte

An examination of thin sections of the freshest granite avail~

able shows the rock to consist essentially of anhedral grains of

feldspar and quartz together with aggregates, irregular in

out-line, of small hornblenqe grains Both feldspar and quartz s,how

wavy extinction, which suggests that the rock has been

subJect-ed to considerable pressure This suggestion is further borne out

by the study of quartz grains Rounded outlines.o~ quartz g~'ains

which appear in ordinary light to have been, orIgmally, a smgle

grain are found, when examined in polarized light, to comprise

an aggregate of smaller grains Such quartz grains are always

traversed by numerous trains of dusty inclusions The most

abundant feldspar in the slides is orthoclase, usually as twmned

crystals Some decomposition product occurs along cleavage

cracks as small scales, perhaps sericite Although most of the

microcline is present as large phenocrysts, ~s mentioned in a

preceding paragraph, a subordinate amount is present as sn;aller

grains It shows the usual tWinning according to the Perlcline

law, and is remarkably free from decomposition Crystals of

acid plagioclase, either with subhedral outlines or in

well-de-fined crystals, are quite common in the rock The effect 0

polysynthetic twinning, very fine, narrow striations on cleavage

faces is a characteristic feature By optical means, this mineral

was found to be albite Aggregates of small scales of a micace~

ous mineral (sericite or paragonite) occur in the feldspar A

a rule the albite shows more decomposition than any of the oth

er feldspars Frequently only small areas of a grain remain~re

from alteration Hornblende is present as an aggregate of grams,

roundedlor irregular in outline The hornblende is of the

green-ish variety, strongly pleochroic, with the character~sticcleavage

It shows some alteration to fibrous shreds of chlorIte

Among the accessory minerals are magnetite, pyrite, apatite,

and zircon The magnetite occurs as veinlets traversing the

hornblende or moulded around grains of this mineral, indicating

that its period of formation was slightly later than that of the

hornblende Associated with magnetite are occasional grains of

pyrite Apatite occurs as rather large; stout crystals, usually en~

closed in the magnetite or the hornblende Smaller crystals of

this same mineral, as slender needles, may be observe~ in bot

feldspar and quartz Well crystallized individuals of ZIrcon are

also common but no titanite was found Very small needles of a

yellowish br~wn mineral in the feldspars may be rutile, but i

was not positively identified

24

THE OATMAN AND KATHERINE DlSTRICTS 27

7 Op cit p 34 SOp cit p 37

Op cit p 17.

e basic end of the series and rhyolites at the acid end Between

he extremes are various intermediate types

'rhe lowest member of the series was described by Schrader as

he "basal andesite" or the "older andesite."7 Above, is an

·tic flow to which Schrader gave the name "green chloritic ite," and still higher in the series is his "undifferentiated vol-anic rocks."s Ransome, however, mapped the district in detail

ande-nd separated the various members of the volcanic series; aande-nd toese members he gave formational names His terminology,ased on more detailed studies, gives a more accurate classifi-tion of the rocks of this interesting series

In the western part of the Oatman District, the basal memberthis volcanic series rests on the pre-Cambrian rocks or on theurdock breccia In the southeastern part of the Katherine Dis-ict, a flow of trachyte, correlated with the Alcyone, rest inlaces on the Katherine granite At other places in this district

he flow is underlain by a bluish-gray tuff, which in turn rests on

he granite Exposures fail to indicate the topographic relief at

he time volcanic activity began Itappears to have been hat hilly with some of the depression filled or partly filled with

some-e dsome-etritus that forms thsome-e Murdock brsome-eccia

A search of the various tuffs intercalated in the flows failed toield fossils In many parts of the Great Basin Province, fromorthern Nevad~southward to the Mexican boundary, volcaniccks are commonly found At some places, the occurrence ofossils' in associated tuffs shows the volcanic rock to belong to

he Tertiary period, and the various flows and associated rocks

t Oatmaan are also believed to be T'ertiary' in age

The volcanic rocks dip to the eastward at a low angle; theIdest members, therefore, occur to the west and form irregularelts with, roughly, a north-south trend To the eastward andrming the crest of the range, are the younger members of theries

as been named by Ransome fhe Alcyone trachyte.9 In general

he color of the Alcyone trachyte, when viewed from a distance,

a delicate lavender tint; occasional areas are pale greenishray Some flows are reddish, perhaps due to the oxidation of

he ferromaganisan silicates, while others, more basic in osition, are of a rather dark gray Interbedded with the flows

com-ARIZONA BUREAU OF MINES

TERTIARY LAVAS

In the Black Mountains of western Mohave County is an

sive series of volcanic flows, agglomerates, and tuffs which sho

considerable variety, in composition and texture These flow

and associated tuffs are of such diverse types as olivine basalt a

No substance of this nature was observed anywhere in th

Katherine District Although it may have been presentbeneatl

the lavas at one time, it has probably, like the lavas, been re'

moved long ago by erosion

The absence of sorting, the angularity of the boulders an

smaller grains, and the freshness of some of the feldspar sugges

the materials of which this formation is made up V1;~retrans

ported by streams, torrential in character It is possible tha

arid or semi-arid climatic conditions prevailed at the time 0

decomposition

The age of this breccia is uncertain No Paleozoic or Mesoz6

sedimentary rocks occur in the region The nearest exposur

of Paleozoic rocks, which are of marine origin, is approximate

sixty miles to the northeast in the Grand Wash Cliffs Itis po

sible that these sediments covered this region at one time T

upper Cretaceous sediments of eastern Arizona with their co

tained coal bed indicates a humid climate If, therefore,

assumption is correct that the Murdock breccia was formed

del' semi-arid conditions and cannot be correlated with any ()

the formations already mentioned, it was, most probably, d

posited at some time during the Tertiary, perhaps early Ted

ary

Fig 6.-General view of the town of Oatman from the south The white

in the lower central part is the tailing pile of the Tom Reed mill.

26

N a,O _ _ " , _ _ 4.23 K,O _ _ _ 6.30

H 2 0 above lloac _ _ _._._ _ .34 H20 below Hoac _ _ _._ -._ 47

The framental members, in part, show sorting and distinctstratification, but larger fragments of rock are to be seen hereand there mixed with the finer debris A microscopic examina-tion shows aD abundance of glass shards together with angularfragments of the minerals commonly found in these rocks

Exposures of stratified sands, grayish in color, with a ness of sixty feet, are present less t'han a quarter mile due south

thick-of the White Chief Mine Part thick-of this 'material is coarser in ture and is composed of angular fragments of the :Alcyonetrachyte, which may be the products of explosions

tex-In the narrow valley south of the Vivian Mine is an exposme

of detritus; derived by weathering from Alcyone trachyte andtransported by stream The bedding, in places quite distinct,dips to the east ail 17 a to where it is overlain by the Oatmanandesite At this place, the measured thickness is 310 feet

In a saddle immediately east of the Boundary Cone, the cyone trachyte has a: brownish color, and is overlain by thetufaceotis member at the base of the Esperanz?- trachyte Nosedimentary material occurs at this point

Al-Itappears, therefore, that the Alcyone trachyte was subjected

to some erosion before the tuffs and flows of the Esperanzatrachyte were formed How extensive this erosion was is not

ARIZONA BUREAU OF MINES

28

are beds of ash and volcanic agglomerate The differences in

color give a banded appearance to the formation in some places,

The Alcyone trachyte is composed of rather thick, massive

flows, but in places they! show a platy structure In a hand

specimen, the rock invariably shows an abundance of stubby

feldspar crystals and, occasionally, ferromagnesian constituents

in a dense groundmass Some of fhe flows are really flow

brec-cias formed by the breaking up and inclusion within the

moving magma of the thin solidified crust This type is par~

ticularly well exposed to the south of the Boundary Cone rhyo_

litic plug

The maximum thickness of the Alcyone trachyte was estimat

ed at about 2,000 feet for exposures in the vicinity of Fortun

Hill, to the west of the Leland Mine The flows are little disturb~

ed by faulting, and the estimate is believed to be close to the ac"

tual thickness The thickness varies from place to place,

prob-ably due to erosion At the United Eastern Mine, as shown b

diamond drilling, the andesites rest directly on the old granite

When examined in thin sections, the Alcyone trachyte sho

some variation in mineral composition The phenocrysts of felc

spar are commonly orthoclase, but in the more basic membed

the phenocrysts are andesine Smaller plagioclase crystals are

always of a more acid variety of andesine than the phenocrysts,

The groundmass contains an abundance of small feldspar laths,

which, in specimens not too intensely altered, were determined as

orthoclase The ferromaganesian constituents also vary in the

different flows; the more acid members show biotite, somewhat

aLtered, and outlines of what appears to have been hornblende

The basic flows contain augite and occasional remnants of

horn-blende Magnetite grains and apatite needles occur as accessory

minerals The groundmass is glass crowded with minute crystals

of feldspar and dusted with grains of magnetite The texture is

vitrophyric with well-defined flow lines

The larger orthoclase crystals are commonly altered along

cracks to a white, opaque substance, perhaps kaolin The

plagio-clase shows more intense decomposition than the potash

feld-spar and consists of aggregates of small scales of sericite some

calcite, secondary quartz, and, less commonly, a little epidote

Of the ferromaganesian constituents, the augite shows the least

alteration The hornblende is usually entirely replaced by

cal-cite, serpentine, bastite, and secondary quartz These minerals

are frequently surrounded by a rim of magnetite and' hematite

which outlines the original crystal The groundmass is clouded

with kaolinitic dust

known, nor is it definitely known that actual disturbances took

place after the volcanic activity that gave rise to the Alcyone

trachyte

to the southwestern part of the Oatman District, and rocks of a

similar character were not observed anywhere in the Katherine

District The limited distribution may be due to the original

small areas covered at the time the flows were erupted rather

than to erosion following their solidification Where the Oatman

andesite may be seen resting on these trachytes, a small

thick-ness of ash beds is present, but 'no evidence of extensive erosion

East of the areas of Esperanza trachyte s'hown on the map of the

district, the rock is known to extend beneath the andesite to the

Sunnyside Mine where it forms one wall of the Sunnyside fault

on the 500-foot level

The maximum thickness in the block to the northeast of Iowa

Canyon, based partly on measurement and partly on estimate, is

between 800 and 1,000 feet This block, apparently is 'not cut by

transverse faults It is uncertain whether this section contains

more than one flow In hand specimens, the rock is everywhere

remarkably uniform in texture and mineral composition, but a

banded structure which is evident in cliff sections, may mark

the divisional planes between flows; if it does, there are at least

three flows and one bed of volcanic agglomerate An

interest-ing feature of this rock is the manner in which it weathers into

thin slabs, usually somewhat curved It is not uncommon to

find such slabs up to twelVe inches or more in length and nearly

as broad, but only a half inch in thickness As the rock

quite dense, such slabs give out a metallic ring when struck with

a hammer This has frequently led prospectors erroneously to

refer to this rock as a phonolite

The base of the Esperanza, trachyte near the Boundary Cone

is a fifteen-foot bed of well stratified, cream colored ash No

fragments of foreign rocks occur in this tuff, but some layers

are largely made up of angular fragments of pumice, somewhat

lighter in color than the remainder of the ash Just south of

the White Chief Mine, the tuff is between fifteen and twenty feet

thick and has a pinkish color with a mottled appearance due to

the presence of fragments of white pumice Here the tuff rests

on the sandy beds that form the top of the Alcyone trachyte at

this locality

When examined in thin sections, the tuffs are found to consist

largely of glass shards, angular grains of clear feldspar

(sani-dine), and an occasional grain of plagioclase Biotite is

surpris-ingly scarce in the tuff, considering its abundance in the flows

THE OAT1VIAN AND KATHERINE DISTRICTS 31

The glass shards may have been decomposed by hot vapor or lution, for locally a microscopic thin section contains an abun-dance of calcite, some small veinlets of quartz, and a sprinkling

so-of iron oxide

The Esperanza trachyte is a rock which varies in color frompurplish brown to bluish gray and contains small crystals offeldspar, rarely exceeding one-tenth of an inch in length.Abundant flakes of biotite, or black mica, are common in a densegroundmass

When examined in thin sections under a microscope, thephenocrysts of feldspar were found to be mostly the clear variety

of orthoclase, sanidine, with an occasional grain of acid clase The biotite is present as long flakes rather than as themore common hexagonal plates The groundmass, whic'h con-tains very little glass, is closely crowded with long, slender,twinned crystals of feldsPar together with minute grains ofmagnetite It shows a trachytic texture with the flow lines inthe lava indicated by the more or lessi parallel arrangement ofthe small feldspar laths

plagio-No analysis is available of this type of rock The mineralcomposition, however, indicates that the flows of the Esperanzatrachyte are, perhaps, more nearly true trachyte than those ofthe Alcyone The tuffs at the base of the flows contain consider-able calcite, however It is possible that this calcite is from anextraneous source, and should, therefore, not be considered inestimating the probable composition of the rock If, however, itwas actually derived from the decomposition of the glass thenthe rock must approach a latitic trachyte in composition rath-

er than a true trachyte

im-portant of the various groups of flows from an economic point, for it is in this formation that most of the ore in the Oat-man District has been found It forms a continuous belt fromthe southern limits of the area mapped northward to the Oat-man Amalgamated Mine, and exposures of the andesite wereagain observed at the Mossback Mine No rocks of this kindoccur in the Katherine District The belt attains its greatestwidth just west of the town of Oatman where the greater width,along this east-west line, is due in part to duplication in the sec-tion by faulting, but it is 'here also that the Oatman andesite at-tains its greatest thickness As shown by diamond drill holes,the thickness must be around 2,000 feet, perhaps even 2,200 feet.There is a, thinning to the southwest, for, near the HighlandChief Mine, the andesite is not over 600 feet thick North of theMossback Mine, the andesite is also rather thin

stand-ARIZONA BUREAU OFMINES

30

Surface exposures of this rock weather to disintegrated grains

or fragments o.f an olive drab to brownish color Exposures of

harder rock are usually dull green or greenish gray while fresh

rock is of a, dark gray to black color As much of the Oatman

'andesite is altered at the surface, it is frequently difficult in

places to distinguish the andesite from certain more basic phases

of the Alcyone trachyte It is particularly difficult to do so TIE'ar

the eastern margin of the Times porphyry

Where the Gold Road latite has been altered by mineralizing

solutions, as near the Gold Ore Mine, or near the Big Jim, it

closely resembles the Oatman andesite; but the latite always

contains abundant flakes of brown biotite, and remains of this

mineral, even though much altered, can nearly always be found

This is a useful criterion in distinguishing the Gold Road latite

from the Oatman andesite

Near the hl3ad of Iowa Canyon, the andesite may be seen resting

on the Esperanza trachyte with only a few fe~t of reddish ash

beds between the two Northwest of the Pioneer Mine are

well-bedded layers of sandstone and shale which appear to be made up

largely of material derived from the weathering of volcanic

rocks Some thin layers of dark limestone, rarely more than a

few inches thick, occur in the shaly portions No fossils were

found in these limestones which are probably of fresh water

origin

Although the flows which make up the Oatman andesite are

quite uniform in texture and color, some portions show an

un-usual development of large, porphyritic feldspar crystals It is

possible that this rock may occur as an intrusive sill Ordinarily,

the feldspar crystals visible on a fresh fracture are less than a

quarter of an inch in length With a hand lens, some pyroxene

may be seen, but in none of the rocks examined was biotite found

in a hand specimen The groundmass in which the crystals are

set is quite dark in color and dense in texture

The individual flows rarely have a thickness of over 100 feet

This fact is brought out in tile examination of diamond drill

cores An amygdaloidal texture is well developed at the tops of

the flows and perhaps, also, to some extent at their bases The

vesicular portion at the tops of the flows not only has a greater

thickness than that at the bases, but in most flows is stained

reddish due to the oxidation of the iron Some of the cavities

in such vesicular portions are lined with a thin film of greenish

chlorite, and, resting on the chlorite, is a thin film of scaly

hem-atite When tb,e cavity is filled with introduced matter these

irregularly rounded lumps of mineral are referred to as

amyg-dules, and· the texture of the rock is then known as amygdal-)

?idal The amygdules are commonly composed of calcite which

IS usua.II! surround~dby a rim of chalcedony Some of the

small-er c~vItIes are entIrely filled with chalcedony The vesicular

pOl'tIons of the flows are more altered than the main body ofthe rock

A.mi<;rosc?pic examination of these andesites shows little versIty m mmeral composition In many thin sections, the min-erals are too alt.ered for accurate determination The largercrystals of pl.agIOclase vary in composition from andesine tolabradorIte wIth the central portion of the crystal more basicthan the margins Much of the feldspar is altered to calcite and

(augIte) a.nd brown b.IOtIte, both of which are largely altered

to serpe.ntme or ~hlorIte Na hornblende was noted in any ofthe sectIOns Grams?f magnetite and slender prisms of apatiteoccur as accessary mmerals The groundmass is rather denseand is cl.ose.ly packed with microlites of feldspar some of whichshow twmnmg and h~ve ~ low index of refraction Itis possiblethat some of these mIcrolItes are orthoclase which would accountfor the rather high potash content found by analysis in some ofthese rocks

The porphyritic texture is quite pronounced but there is siderable variation in the proportion of phen~cryststo ground-

con-mas~ In some specimens, the large crystals are embayed,

sug-gestmg resorptIOn by the magma, but most of them still showwelt-developed crystal boundaries This is true also for some ofthe pyroxene crystals, but occasionally the augite occurs as acluster of irregular grains In the groundmass of some speci-mens, the microlites of feldspar show a more or less parallel ar-range:nent, indicating flow lines Perhaps these varieties of theandesIte are more acid in composition

The analyses below are from Ransome'sl/ bulletin and fromSchrader's12 report

33

4.00 2.60 5.19

4 56.33

7.96 2.43 3.13

3 53.13

5.60 2.62 3.14

2 53.55

ANALYSES OF OATMAN ANDESITE

THE OATMAN AND KATHERINE DISTRICTS

11 Op cit p 23.

Op cit pp 36-37.

ARIZONA BUREAU OF MINES

32

No.1 is given by Ransome as an analysis of the specimen from

the No.2 shaft of the United Eastern R C Wells, Analyst

Nos 2 to 4 are partiaI analyses from Schrader's report No

2 is from the west Gold Road Mine; No 3 from the Pasadena

Mine; and No.4, is from the lower east tunnel of the Leland

Mine E C Sullivan, Analyst

In these analyses, the alkali content is somewhat higher than

is to be expected in typical andesites This is particularly true

of the specimen from the Leland Mine This rock is classed by

Schrader as latite, and correctly so, althoug'h he recognized it as

forming a part of his "green chloritic andesite." The others

should be classed as latitic andesites

Volcanic agglomerates are intercalated in the flows at various

places Near the head of Iowa Canyon is an excellent exposure

of such material which consists of angular fragments of

ande-site, decidedly vesicular in texture and stained reddish due to

the oxidation of the iron compounds Some material of this

nature was also noted on Silver Creek, near the Nigger Head

Ransome13 mentions the occurrence of tuffaceous sandstones

to the southwest of the Argo Mine, and somewhat similar

sand-stones were found on the 900-foot level at the BI:ack Eagle shaft

where the tuffaceous member has a known thickness of 270 feet

An interesting feature is the occurrence of angular fragments of

rhyolite up to ten inches in length This rhyolite contains visible

crystals of quartz and feldspar in a groundmass showing

pro-nounced flow banding No flows of this character older than the

andesite are known in the Oatman District, although it is

pos-sible that such a flow may be covered by some of the later rocks

The source of these fragments is, therefore, unknown

Road latite which is apart of Schader's "Undifferentiated

Vol-canic Rocks"14 to which Ransome 16 gave the formational name

Gold Road latite The higher members of the series are rhyolites

which Ransome proposed to map separately for his final report

These flows form the rugged cliffs to the east of Oatman and apart of the surface rock of the mesa extending for some dis-tance to the east To the south of Oatman, the latite is cov-ered by the basalts of Ute Mountain These flows are exten-sively exposed north of the Gold Road fault, and extend an un-known.dista~ce ~o the north South of the area mapped in the

Kathe~me l?l~trIct are some flows belonging to this period ofvolcamc actIVIty They are well exposed a short distance to thewest of Thumb Butte

The Gold Road latite shows some variations in thickness Whatappears to be the thickest section exposed occurs to the east of

Oatma~ Here, however, there is considerable faulting, and thetrue thwkness IS not known as the throw on the various faultshas not been determined These flows dip to the east from 80

to 12° In the cliff section alone, the flows and associated tuffshave a combined thickness of over 1,000 feet The minimumthickness is estimated at 1,600 feet Part of the variation inthickness may be due to a rather limited distribution of individ-

there IS not over 600 feet of latite in the cliff section T:here hasbeen some erosion of the original surface, for the tuff at thebase of the overlying, rhyolite may be seen occupying depres-sions An excellent example may be seen to the southeast of theSunnyside Mine, and similar, pre-rhyolite erosional featuresoccur near the head of Antelope Canyon Some flows ratherdistin~tiv:ein appearance, which are abundant in other ~arts ofthe dIStrwt, do not occur here As a rule, the flows are rathermassive, and many individual flows have a thickness measured

in hundreds of feet

The contact of the Oatman andesite and Gold Road latite isnot always well exposed A few feet of ash beds are usually allthat separated these two types of rock At Iowa Springs thebase of the latite is a volcanic agglomerate about eighty' feetthick that contains an abundance of large and small boulders set

in a matrix of finely divided ash Nowhere was any definitelysedimentary material noted between the two formations Theandesite does not appear to have suffered much erosion, whichwould suggest that perhaps the interval of time between theerupting of the andesites and latites was rather short

As a rule, the various flows are some shade of gray or brownand the dull greenish color so characteristic of a weathered sur~

face of the underlying andesite is entirely absent It is onlywhere the latites have been intensely altered by mineralizingsolutions that they cannot be distinguished from the andesites

35

THE OATMAN AND KATHERINE DISTRICTS ARIZONA BUREAU OF MINES

34

Op cit p 39.

The basal member of the latite is well exposed in a small hill to

the south of the Texas shaft Itis darker in color than most of

the flows, being a dark gray with a lavender tint Somewhat

higher in the series the latite flmys are alight gray, and, towa~'d

the top of the cliff, the latite is brownish Such flows are

dIf-ficult to distinguish from the rhyolites

The latites always contain large, well-developed, tran~parent

crystals of feldspar These phenocrysts are larger than IS

com-mon in either the andesite or the rhyolites Many of these lar!Se

tabular crystals are rounded in outline Sparkling fla~es of

bI?-tite are always present Pyroxene may be seen WIth the aId

of a hand lens, and a glassy variety of latite, near the top of the

mesa, contained visible crystals of hypersthene The groundmass

Examined in thin section, these latites show only shgh~

?Iffer-ences in mineral composition The larger phenocrysts vISIble to

the unaided eye are predominantly andesine, a plagioclase

feld-spar intermediate in composition The euhedral cryst~ls of

plagioclase show very little zoning A second generatIOn of

plagioclase is somewhat more acid in composition and has be.en

determined as oligoclase Some orthoclase also occurs as lar.ge

crystals, but is not common Among the ferromagnes.ran

mm-erals biotite of a deep brown color is a constant constItuent of

thes~ lavas Common augite, pale green in section, is also

near-ly always present It frequently shows well-deve~oped crystal

boundaries both in section parallel to and perpendIcular to the

vertical axis In some slides, the augite occurs as an aggregate

of rounded grains One slide showed green hornblende pa.rtly

surrounding the pyroxene A glassy var.iety of latite c~ntamed

hypersthene in addition to augite Grams of m~gnetIte and

slender crystals of apatite occur as accessory constItuents The

groundmass may be closely crowded with minute, uI,1twm~ed

feldspar laths, or it may be composed larg.ely o~ glass m w:hlCh

incipient crystals, trichites, are visible WIth hIgher ~ag.lllfica­

tion Perlitic cracks are common in the glassy vanetles of

Analyses of the latites show greater differences in composl Ion

than are apparent in a study of thin sections The two analyses

given below from Schrader's report are classed as trachyte, 16

al-though they were collected from underground at the Gold Road

Mine To the northeast of this mine, Ransome has mapped tw.o

trachytic lavas which are later in age than the latite The

speCI-mens collected by Schrader may be intrusive sills formed at a

37

3 66.46 14.14 4.07 40 67 78 1.26 9.26 78 1.28 83 25 03 05

None

.06 03

2 58.74 15.09 4.66 84 2.75 2.68 25 8.05 2.08 3.0'9 98 40 09 02 61 07 04

1

62.96 15.36 2.57 2.09 2.50 4.26 3.84 3.96 23 1.37 72 28 04

THE OATMAN AND KATHERINE DISTRICTS

ANALYSES OF GOLD ROAD LATITE

No.1, R C WELLS, Analyst.

Nos 2 and 3, E C SULLIVAN, Analyst.

time when the later trachytes were erupted Again, they may

be the result of alteration by mineral solutions as suggested bySchrader

and tuffs are confined to the higher portions of the range Themap of this district includes only the western edge of the highercountry, consequently only erosional remnants of these acid lavasremain North of' Sitgreaves Pass are extensive exposures ofrhyolite which have been separately mapped and named by Ran-some as the Cottonwood rhyolite The Sitgreaves tuff which un-derlies the black glassy flows of rhyolite to the north of the passare not present south of this pass No rock resembling the Sit-greaves tuff occurs in the upper reaches of Antelope Canyon, and

different in appearance It is not definitely known, therefore,that the Cottonwood rhyolite and the Antelope rhyolite wereerupted at the same time The southernmost exposure of therhyolites noted was about a mile to the northeast of IowaSprIng

Rhyolite tuffs are abundantly exposed in the range to the north

of Oatman and extend even beyond Union Pass In the eastern

ARIZONA BUREAU OF MINES

36

Op cit p 26.

ANAL,YSIS OF RHYOLITE

R C WELLS, Analyst.

A120• 13.36 H 20 above llooe , 3.43

THE OATMAN AND KATHERINE DISTRICTS

18 The alteration of the rocks produced by the solutions forming th~

veins will be discussed in the section on ore deposits.

Volcanic eruptions, particularly of the more violent type, arealways accompanied by the emission of great quantities of gas,among which water vapor is the most abundant constituent

- ALTERATION OF THE LAVAS18

northeast corner of the Oatman District, and no rock resembling

it occurs in the Katherine District As shown by Ransome'smap, this tuff underlies the Cottonwood rhyolite At SitgreavesPass, the tuff rests on the Gold Road latite, and to the northeast

it rests on trachytes younger than the latite Exposures to thenorth of the highway to Kingman, just east of Sitgreaves Pass,form prominent, light colored cliffs, and there the beds of tuffare quite massive and compact

On a fresh fracture, the tuff is ligl1;t-gray in color and ers buff The rock is somewhat porous, and consists of frag-ments of pumice together with crystals of sanidine, biotite, andoccasionally hornblende Some rounded grains of quartz may beseen under the microscope

weath-The Sitgreaves tuff would make an excellent building stone.Because of its porous nature, it is the water-bearing formation

of the district It is from, this rock that nearly all ~he springs

of the district issue

are extensive flows of olivine basalt Only a sman portion ofthese flows is shown in the southeast corner of the map of theOatman District A few erosional remnants occur a short dis-tance south of Sitgreaves Pass, capping the rhyolite flows Ex-posures of these basic flows also occur to the north of this pass

At the base of the flows are beds of bright red volcanic ash.The basalts are dark gray to black in color and fine-grained intexture Some of the flows are quite vesicular in texture, and thecavities in places are filled with calcite With a hand lens bothplagioclase feldspar and olivine may be identified In thin sec-tions, the rocks show no unusual features, and the mineralspresent are basic feldspar, olivine, augite, and magnetite.Just north of Union Pass, and capping the higher points, arealso basaltic flows Th,ey are slightly east of the limits of thearea mapped as the Katherine District The flows are black,quite dense in texture, and are interesting because they areslightly different in mineral composition from those in the Oat-man District They are the olivine-free variety of basalt

ARIZONA BUREAU OF MINES

part of the Katherine District are erosional remnants of both

flows and tuff There the tuffs attain a much greater

thick-ness than in the Oatman District

The rhyolites show some differences in appearances; in some

places, they are black obsidian with transparent crystals of

sani-dine and shiny flakes of biotite; inother localities, the obsidians

are pale gray glass with bright red spherulites Very

common-Iy these glasses show a streaked appearance or flow banding

Many of the flows are of a reddish brown color with crystals of

feldspar, quartz, and biotite in a stony groundmass

Examined in thin section, these rocks show' crystals of

sani-dine, acid plagioclase, and brown biotite Clear crystals of quartz

are common and usually show resorption by the magma

Occa-sional crystals or grains of green hornblende or of nearly

color-less augite may be seen Grains of magnetite or needles of

apa-tite occur as accessory minerals Small, rounded crystals of

zircon were found in the flakes of biotite The groundmass of

the stony varieties contains a second generation of minute

feld-spar laths in glass The glassy varieties show an abundance of

perlitic cracks Frequently, hair-like incipient crystals or

trichites are present

At some localities, the tuffs are well stratified The lines of

stratification are more apparent where fragments of foreign

ma-terial are abundant The tuffs may be cream, pink, or dark brown

in color Fragments of pumice or of lithoidal rhyolite are

em-bedded in an aggregate of glass shards Grains of feldspar and

quartz are also present

Ransome 17 gives an analysis of a specimen collected

three-fifths of a mile south of Sitgreaves Pass This particular area

has been included by the present writer with the rhyolites

Ransome classed it with the Gold Road latite, but recognized that

it was much more acid than the typical latite He planned to

map these rocks separately at a later date for his final report on

the district

38

19 Clarke, F W., The data of geochemistry: Bull 770, U S Geol Sur.

vey, pp 261-292, 1924.

Even the quiet outwellings of basalt from fissure eruptions are

accompanied by such vapors Volcanic explosions and their

after-effects have long been an interesting subject of scientific

in-vestigation ClarkeHl gives an excellent summary of the

litera-ture on volcanic emanations, including the classical studies about

the middle of the 19th century These early investigators

noticed that even t'h,e surface of flowing lava gave off white

vapors Some such vapors sublimed to anhydrous salts The

temperature of such flowing lava varies somewhat depending

partly on the composition of the magma Measurements made

at different places indicate llOOGC as an average

The gases enclosed in the magma are, therefore, at high

tem-peratures and under great pressures As the magma rises in

the conduit to the surface, the pressure is released, and the

vio-lent explosions accompanying volcanic eruptions are due to the

sudden expansion of these gases So powerful are these forces

of explosion that, in many eruptions, large quantities of the rock

lining the conduit are disrupted and thrown high into t'h,e

atmos-phere Great quantities of liquid lava are also ejected, and the

expansion of the gas withini this Hquid gives rise to a froth of

glass on cooling In this manner are formed the fragments of

pumice wh~ch settle out of the air to form the beds of volcanic

ash or tuff so common around volcanic vents Much of the

ma-terial of which the tuffs are composed is rather light in weight

and porous in texture, and such ash beds are usually very

perme-able to vapors and solutions

Even the slow-moving flows of lava may develop a vesicular

texture in the upper portion of th,e flow In the acid lavas,

vesicles are generally less abundant, and this condition may be

due in part to the more viscous nature of the magma The more

basic flows, such as andesite and basalt, appear to have been

much more fluid, and the tops of such flows are usually so filled

with cavities that fragments of this vesicular lava will float on

water To the east of Oatman, the rhyolites often contain

litho-physae or stone-bubbles which are spheroidal objects which

consist of thin, concerttric shells, separated from each other by

air spaces Cavities also exist which are more or less filled with

chalcedony or opaL In the Oatman andesite, a vesicular texture

is often well-developed, and, although not commonly seen on a

weathered surface, is clearly and abundantly shown in diamond

drill-cores

41

THE OATMAN AND KATHERINE DISTRICTS

The a~ter-effects of volcanic activity are fumeroles or vents

from ~hICh great quantities of gas issue This feature was well

exemplIfied followmg the eruptions of Mt Katmai in Alaska in

1912 The floor of a valleYI about eight miles from the craterwas filled to ~ variable depth with layers of ash Through these

beds of pumIce, numerous fumeroles issue The gases ill' thisvalley, no~ known as the Valley of Ten Thousand Smokes, have

been studIed by Allen and Zies.20

Clarke21 divides the after-effects of volcanic activity into four

21 Clarke, F W., The data of geochemistry: U S Geol Survey Bull

stages which depend largely on the temperature, as follows:

dry In addItIOn to superheated steam, they may containhydrogen, carbon monoxide, vapors of metallic chlorides,i nitro-gen, sulphur vapor, and gaseous compounds of fluorine Someoxygen may be present

2 The hydrogen burnE\ to form water vapor which in turn

re~cts with the metallic chlorides to form hydrochloric acid, and

~cld fumeroles result The sulphur burns to form sulphur

diox-Ide, and carbon monoxide to carbon dioxide

3: These acid gases traverse and penetrate the rocks throughWhICh they pass and react with the minerals of the rock pro-

4 The dying stages of fumerolic activity emit only steam andcarbon dioxide

Tha~ the vapors of fumeroles are capable of producing intense

alteratIOn m the rocks traversed has been shown by study atnumerous places

In both the Oatman and Katherine districts the lavas oftenshow intense alteration which does not appea~' to have beenbrought about by the solutions that formed the veins Such al-teration is not due to surface weathering and oxidation for itoccurs at considerable depth below the surface It appears there-fore, that the alteration may have been caused by the gase~ which

passed through the rocks Some members of the volcanic seriesshow more pronounced alteration than others This alteration

is best exemplified in the Alcyone trachyte, while the overlyingEsperanza trachyte is remarkably free from alteration In theOatman andesite, this type of alteration is confined to a narrowedge along joint planes or other fractures in the rock and to the

vesicul~r port~ons of the flows Both the latite and rhyoliteshow lIttle eVIdence of decomposition except along joints, but

• 20 Allen, 'E T and Zies, E G Nat Geo Soc Tech paper Katmai

ARIZONA BURFJAU OF MINES

40

the tuffaceous members associated with these flows invariably

s'hpw some change

A geologist who examines the Alcyone trachyte is

immediate-ly impressed with the extent of the decomposition that has

af-fected this rock Specimens'coming from a depth of over 500

feet below the surface show these changes to the same degree as

do pieces from nearer the surface A hand specimen of this rock

usually appears to have been bleached;- the feldspars are

kaolin-ized, and the ferromagnesian constituents are either altered to

chlorite or else the iron is abstracted and segregated as

magne-tite The outline of original hornblende crystals is usually weIl

shown by a narrow rim of magnetite which also contains, in

some cases, hematite; and within this rim of iron oxide is pale

greenish chlorite or serpentine with some calcite Feldspars are

largely changed to aggregates of kaolin, secondary quartz, and

small amounts of calcite The groundmass of the rock is

frequent-ly so clouded with kaolin that portions of the slide are quite

opaque There is no evidence in the thin sections to indicate th~t

the feldspars were first altered to sericite and this mineral m

turn changed to kaolin, although a little sericite was found in

The interesting fact that the overlying Esperanza trachyte

has suffered no such decomposition indicates that the alteration

was produced prior to vein formation Itis possible, therefore,

that the mineral changes in the Alcyone trachyte were produced

by hot gases sh,ortly after the consolidation of the lavas

The most interesting changes in the Oatman andesite occur in

the vesicular portions of the flows Where the vesicles are

abundant and close together, the wall of rock between

individ-uaL bubbles is quite thin; consequently, when such rock has

un-dergone more or less decomposition, it is so soft that it can

readily be crushed in the hand The altered rock is nearly

al-ways of a pale greenish color except in those portions in which

the iron h~s been oxidized, and then the rock is reddish

These altered rocks, when examined with a.microscope, show

intense changes in the original minerals Of ,the feldspars, the

orthoclase which is not abundant, always sJl,ows less alteration

than the ~lagioclase. In the orthoclase, some kaolin may be

seen along cracks in the mineral, but the plagioclase is largely

replaced by calcite and a little quartz The ferromagnesian

constituents, unlike these constituents of the Alcyone trachyte,

are not outlined by magnetite; instead, the change has been

largely to serpentine Now and then unaltered remnants of

either biotite or augite may be seen

TERTIARY INTRUSIVE ROCKSTwo major intrusions are associated with the volcanic activity

of Tertiary age that gave rise to the flows and tuffs in the man and Katherine districts Numerous dikes and sills showingnearly as much variation in composition as the flows themselvesoccur as minor intrusions in the flows No dikes which corre-

Oat-Whereth~ vesicles have been filled with mineral matter they

sh?w a defimte sequence The partly filled vesicle is lined with athm film of a scaly green mineral, chlorite Resting on the chlo-rite are scales of bright red hematite This mineral is not how-ever, alway~ deposited If the cavity is of small size, it maythen be entIrely filled with chalcedony, but usually the centralportion is composed of calcite The groundmass, invariably, con-tains an abundance of kaolin

Alteration of the rhyolites is confined to a thin film along joint

~lanes Along these joints, chalcedony and, in some cases, opal

IS deposIted As the tuffs are more pervious to hot vapors Or

solu~ions, they contain an abundance of kaolin, and, in part, thiskaolm has been formed from the decomposition of the glassshards

To sum up: The important changes are hydration and nation This fact is indicated by the abundance of chlorite andserpentine, both, hydrous minerals formed from biotite, augite,and hornblende, and the presence of kaolin formed from feld-spar No analyses of the altered rocks are available, and it is,therefore, not possible to say to what extent certain constituentslike soda and potash have been abstracted and carried away Thefact that orthoclase is replaced by kaolin indicates that potashhas been removed; and, similarly in the plagioclase soda has• , I · ,dIsappeared That constituents have been transferred is clear-

carbo-Iy shown by the film of chlorite and, sometimes, hematite whichlines the vesicles in the andesite There is no evidence in slidesthat silica has been introduced, and such irregular aggregates ofsecondary quartz as occur within or surround altered mineralsmay have been formed: by the breaking down of silicates; norcan one definitely say that lime has been introduced Such limeas! is now found in the form of calcite could easily have comefrom the breaking down of hornblende, augite, and plagioclasefeldspar Carbon dioxide was, however, certainly introducedfor it is hardly possible that the fresh rock contained sufficient

of this gas to form the amount of calcite existing in the alteredroc.k.Carbon dioxide is abundant in fumerole gases, particular-

ly m the later phases of their acivity

43

THE OATMAN AND KATHERINE DISTRICTS ARIZONA BURFJAU OF MTNES

42

spond in composition to the Alycone and Esperanza trachy~es

were found but dikes of andesite are common; such andesIte

dikes are, however, difficult to trace where they cut the andesite

flows Only a few dikes were observed which appear ~o have

been the feeders that gave rise to the latite flows DIkes of

rhyolite-porphyry are common in both the Oatman and

Kather-ine districts In some instances,' there has been movement along

these dikes after consolidation, and vein filling is frequently

found in such fractured zones

MOSS PORPHYRY

Exposures of the Moss porphyry occur about a mile to the

north of the Hardy Mine and extend northward to beyond the

Moss Mine The average width of this intrusion is about two

miles, and it has a known length of somewhat over four miles

The general trend is towards the northwest

Just west of the Moss Mine, this porphyry intrudes the Alcyone

trachyte and the flows have been tilted to the west at angles as

steep as 40° North of the Oatmallt District, the porphyry was

observed cutting the Oatman andesite Where the Moss porphyry

is in contact with the flows of Gold Road latite, the rocks are so

thoroughly altered that the relations are not absolutely clear

The Moss porphpry consolidated, therefore, after the flows of

anadesite were poured out, and perhaps later than the Gold Road

latite

Fresh exposures of the rock are of a grayish color due partly

to the ferromagnesian minerals present and also to phenocrysts

of palgioclase feldspar which are of a d,ark gray color Altered

rock varies from a creamy white, freqently iron-stained, to a

pale greenish gray The rock is porphyritic in texture :vith

phenocrysts of plagioclase crystals up to one-quarter of an mch

in diameter These phenocrysts, somewhat rounded in outline,

are thin plates of a dark grayish color Polysynthetic twinning

may be observed with th)e aid of a hand lens The groundmass

is uniformly fine grained in texture, pinkish in color, and appears

to be largely orthoclase A little biotite and quartz may also be

seen in the rock

A thin section of the rock examined' under the microscope

shows more alteration than is apparent in a hand specimen The

plagioclase, which has the composition of acid andesine, is altered

along -cleavage cracks and fractures to an aggregate of scales

of sericite The orthoclase is quite turbid and has -been

re-placed almost entirely by a felted mass of sericite Biotite is

partly ll.ltered to chlorite Quartz is not abundant III the rock

to a dull brownish color, but fresh exposures are light gray with aslight pinkish tint The rock is not conspicuously porphyriticalthough a close examination discloses phenocrysts of orthoclaserarely more than one-quarter of an inch in length Occasionalthin flakes of biotite may be seen, as well as some pyrite whichwas introduced after the magma solidified The groundmass isuniformly fine grained, and, in this groundmass, quartz is visibleunder a lens

The most striking feature observed in a thin section is the tergrbwth of quartz and feldspar of the groundmass, forming amicropegmatitic texture Where this intergrowth surrounds aphenocryst of orthoclase, the feldspar of the intergrowth has the

in-ANALYSIS OF MOSS PORPH\YRY

As was noted by Ransome, this analysis of the Moss porphyry

is similar to that of the Gold Road latite Both the chemicalanalysis and the mineral composition, as shown by microscopicexamination, show the rock to be a quartzlllonzonite-porphyry.The amount of quartz in the rock is somewhat less than is com-monly found in this class of rocks

and occurs either interstitially or intergrown with orthoclase,forming a micropegmatitic texture Magnetite, zircon, theapatite occur as accessory minerals

A chemical analysis of the Moss porphyry made on a samplecollected by Ransome north of the Moss Mine is as follows:22

ARIZONA BUREAU OF MINES

44

Op cit p; 29.

RHYOLITE-PORPHYRY

Dikes of rhyolite-porphyry are common in both the Oatman

and Katherine districts and also in the intervening country In

some instances these dikes are connected with intrusive plugs,

notably the Boundary Cone The white knob east of the town

47

Fig 7.-The Elephant's Tooth, a rhyolitic plug to the east

of Oatman.

THE OATMAN AND KATHERINE DISTRICTS

of Oatman, known locally as the Elephant's Tooth, is the

erosion-al remnant of a dike of rhyolite porphyry at a point where it

is unusuaUy thick The trend of these dikes is in all directionsbut the prevailing strike is either northwest-southeast, or nearl;east-west.some Instances the brecciated wall rock may be seen frozen to. The dikes have been injected along fractures for in'

the dike Fragments of the wall rock are included in the dikes,but such fragments are not abundant and usually correspond tothe volcanic rocks exposed in the district The dikes, as may beexpected, vary considerably in size, and only the more prominentones were mapped These minor intrusives are particularly abun-d.ant near the Times porphyry intrusions, and a local concentra-tIon of them occurs near the Boundary Cone

The prevailing color on a surface exposure is pale brown topinkish and is due to finely disseminated iron oxide but on afresh! fracture, t'bje rock isa creamy yellow The l:ock is por-

ARIZONA BUREAU OF MINES

ANALYSIS OF TIMES PORPHYRY

'i".he small amount of acid plagioclase found in thin sections

would not account for the high percentage of soda shown in the

analysis, and it is possible, as suggesteCi by Ransome, that some

of this soda is combined with potash in the orthoclase The

analysis is therefore that of a sodic granite-porphyry

same optical orientation as the phenocryst A-little acid

plagio-clase was seen in one slide, but the mineral is rather scarce The

feldspar is usually clouded with kaolinitic material, particularly

around grains of pyrite The biotite is more or less altered to

chlorite Scattered grains of magnetite occur as an accessary

The Times porphyry has a rather limited distribution To the

north, this rock does not extend beyond Silver Creek, and the

southern boundary is Times Gulch To the westward, the Alcyone

trachyte has been intruded by the porphyry, but, along the

east-ern margin, the lavas have been faulted against the intrusive

Along Silver Creek, the Times porphyry appears to intrude the

Moss porphpry, but at this locality, the latter rock is so

thorough-ly brecciated and altered that positive identification is

impossi-ble

An analysis of the Times porphyry given by Ransome is as

follows:2 3

46

phyritic in texture with about an equal development of both

quartz and orthoclase The quartz phenocrysts are frequently

irregular in outline, but the feldspar crystals show well-defined

crystal boundaries These crystals are rarely more than

two-tenths of an inch in length

Fig 8.-A genera! view of the southwestern part of the Oatman

Dis-trict The Boundary Cone, a volcanic plug, may be,seen in the center of

the picture.

The phenocrysts of quartz, when examined with a microscope

in a thin section, show a rather stubby development along the

prismatic axis The quartz often shows crystal boundaries, but

here and there it is resorbed and embayed by the magma

Fre-quently a darker border of a finer grain surrounds the crystals

and, if examined with higher magnification, is found to consist

of a micropegmatitic intergrowth of quartz and feldspar The

groundmass is of uniform grain and consists of quartz and

ortho-clase It is interesting, in this connection, to note the occurrence

of such an intergrowth surrounding some of the feldspar crystals

in the rhyolites Dikes of the rhyolite porphyry have been

traced to the very edge of the Times porpryhy intrusion, and, in

other instances, dikes pass up to the contact of the rhyolite flows

The assumption is reasonable that the Times porphyry, the

rhyolite-porphyry dikes and plugs and the rhyolite flows all cam'~

from the, same magma reservoir at about the same time This

observation is important as it throws some light on the time of

in-trusion of the Times porphyry as related to the age of other

igneous rocks As no flows younger than the Oatman andesite

are in contact with, the Times porphyry, its age as compared

with the age of the Gold Road latiteand younger rhyolites could

not be definitely ascertained The dikes may be, however,

con-necting links, between the Times porphyry and the rhyolite flows

49

THE OATMAN AND KATHERINE DISTRICTS

Dark-colored dikes are fairly common in the westel~npart ofthe Oatman District, and they are particularly abundant atFortuna Hill Specimens from this hill were found to be ande-site-porphyry A similar dike was found near the Red Lionshaft, cutting the Oatman andesite As a rule, such basic dikesare difficv.lt to trace in the andesite, and no effort was made tomap them

Dikes, corresponding in composition to the olivine basalt flowswere not observed in the Oatman District It is possible thatthey occur beyond the limits of the area mapped, or they mayeven be entirely covered by the flows

QUATERNARY DEPOSITS

GRAVEL AND SAND

Deposits of gravel and sand are not important in the OatmanDistrict except in the extreme western portion where they coverthe older rocks from which they were largely derived Hereand there, small knobs stand out above the gravel cover, and onesuch k:r:ob in ~heKatherine District contained the outcrop of theKatherme Mme The gravel deposIts are more widespread andhave a greater thickness in the Katherine District than at Oat-man At both the Katherine Extension and the Treasure Vaultmines, it was necessary to sink through the gravel to reach theunlerlying granite In both cases veins were found

T.he thickness of the gravel, as might be expected, is quitevarIable In the flat to the east of the Sunnyside Mine in the

Oatman District, a prospect shaft shows the gravel to be 60 feet

deep Mining operations in the Katherine District penetrated

beds of gravel as much as 100 feet or morein thickness Between

the 'Katherine and Pyramid mines, holes drilled by the tion Service are said to have located an old river channel inwhich these deposits are somewhat more than 300 feet thick.The gravel is composed of angular and subangular to roundedboulders of rock which show considerable variation in size As arule, the coarse deposits show very little sorting, but the sandylayers are sorted and cross-bedded The pebbles and boulderscomprise an types of rock common in the district, and their de-rivation has been local, largely from the mountains to the east

Reclama-On the banks of the Colorado River, however, pebbles ofquartzite and limestone are quite common, and, as no such rocksoccur in th,ese districts, it is possible that such pebbles werebrought down by the river

ARIZONA BURRAU OF MINES

48

Part of the gravels and sands are well consolidated and

some-what cemented with thin films of Mme Locally, such deposition

of calcium carbonate is: in bands which have a thickness

meas-urable in inches, and, in the Southwest, such lime is frequently

referred to as "caliche."

No fossil remains have been found in either the gravel or sand

As the deposits are clearly younger than the lavas, they are here

assigned to the Quaternary

STRUCTURAL GEOLOGY

In a general way, the Black Mountains may be considered as a

tilted block with a fault or series of faults along the western side

The range may also be considered as the eastern limb of a broad

arch, the central portion of which l'ies to the west of the

Colo-rado River If arching of the earth's crust has taken place, the

volcanic rocks th,at Occur on the limbs of the fold may be

con-sidered as the erosional remnants of a vast volcanic field which

originally extended for many miles in all directions Such

arch-ing would give rise to a tiltarch-ing of the lavas< on the limbs, of the

fold There is, however, some evidence, against the idea of

arch-ing, for, at the, Needles, on the Colorado River and a few miles

south of Topock, 'there is no evidence of such arching and the

disturbance in the flow can all be explained by faulting North

of the Katherine District and just west oithe Colorado River, the

volcanic rocks of Eldorado Canyon dip towards the river This

occurrence would suggest that the volcanic rocks of Eldorado

Canyon have been faulted, against the pre-Cambrian rocks to the

east

The best available evidence suggests that the Black Mountains

are a fault block tilted to the east As the maj or fractures in

the Oatman District dip to the east at steep angles, and as these

faults are of the normal type, the crest of the range would be

de-pressed re}ative to the western portion of the district If the

Black Mountains are a tilted fault block, the main fracture, or

series of fractures lies to the west of the Oatman District No

evidence of such a fault was found in the Katherine District,

but much of this area is c,overed with Quaternary gravels

Another possibility that IT).ust be considered is the likelihood

of a fault along the eastern margin of the range The one

oc-currence of pre-Cambrian rocks found there lies at a higher

elevation than the exposures on the western side of the range,

and it is not impossible ~hat the block may have been tilted

along this fault and later modified to its present form by erosion.

Pre-Cambrian granite forms, however, a part of the crest of the

range a few miles to the south of Union Pass, and the old

sur-face on which the lavas were poured may, therefore, have been

quite irregular

The general dip of the lwvas is to the east at low angles South

of the highway to Kingman, the basaltic lavas which form the

very highest parts of the range to the southeast of Oatman are

here at the base of the range The eastward dip is less than five

degrees In the immediate vicinity of Oatman the average dip is

about twelve degrees, but, to the west, it becomes steeper Small

fault blocks may show high dips In the southwestern part of

the Oatman District, the prevailing dip is more nearly south than

east, but here again it is at gentle angles At Union Pass, the

dips observed in the tuff are, in general, similar to those farther

south, but in the region surrounding the Sheeptrail-Boulevard

Mine the small fault blocks dip at various angles

West of the Moss Mine, the lava dips to the west at variousangles up to 240

, and the local westward tilting appears to bedue to the intrusion of the Moss porphyry A somewhat simi-

lar feature occurs around three sides of the Times porphyry It

is not certain that the eastward dip of the andesite and

underly-ing trachyte along the eastern margin 'of the Times porphyry is

due to intrusion of this rock, for here the dip is normal To the

west of Times Gulch the dip is, however, to the south, and, in the

extreme western part of the district, the tilting is to the west

Here again, there is a suggestion that the tilting is due to

in-trusion

To the southwest and also to the west of Mt Hardy, theAlcyone trachyte rests on the Times porphyry The contact is

an intrusive one, and th~ overlying lavas are frequently

dis-turbed and displaced by the ign'eous rock Many faults with a

small displacement occur here, and, on some of them, the

dis-placement is large, as at the main break on which the Times

Mine is located These remnants of Alcyone trachyte are parts

of the original cover over the intrusion

The flows surrounding the Boundary Cone, which is an sive plug, have also been disturbed as a result of intrusion A

intru-more interesting feature is the brecciation produced in the

sur-rounding rocks, which suggests that the magma was injected

un-der consiun-derable pressure and perhaps in a semi~plastic

condi-tion No such features are to be seen in connection with thedikes

53

THE OATMAN AND KATHERINE DISTRICTS

TREND AND DISTRIBUTION OF FAULTS

The general trend of the faults in the Oatman District is west-southeast, but in the southern part of the district they aremore nearly east-west A few faults near the Times Mine (seePlate I) have a northeast trend, but examples of this kind arerare There is no such regularity to trend of faulting in theKatherine District Some faults like the Pyramid KatherineArabian, and Tyro have a northeast trend; othe;s, like th~

north-Treasure Vault, Gold Chain, and Big Four have a northweststrike Itis possible that a number of other faults occur in thisdistrict, but, unless such fractures have been mineralized theyare not likely to be prospected, and, where such fracture; havegranite in both walls, they are difficult to trace The fracturesthat occur in the underlying rock in much of the district are ef-fectively covered by gravel, as at the Treasure Vault and Kath-erine Extension mines

In the Otaman District the faults are grouped in zones eachzone having a slightly different trend Plate I shows a c~ncen­

tration of faults between the Tom Reed vein and the Gold Roadvein In this zone, the average strike is approximately N 45° W.Another area in which faults are abundant lies to the south ofthe Lucky Boy fault and extends westward to include the Vivianand Leland mines The average strike in this zone is about N

600 W To the east of the Boundary Cone is a thir'(j tion of faults with a trend approximating N.70° W These threezones converge toward a point a few miles to the southeast of theOatman District At this point, the surface is covered by flows

concentra-of olivine, basalt, and, as much concentra-of the faulting is earlier than theeffusion of this basalt, the interesting junction of these faults iseffectively covered

,Another interesting feature in connection with these faults isthe prevailing dip To the east of and including the Tom Reedfracture, the dip is generally to the east; while, in the westernand southren parts of the Oatman District, the prevailing dip is

to the southwe8t

There must be some underlying cause for this change of dipfeature An arching of the lavas in a northwest direction acrossthe district with conseql1ent>breaking down of the arch on eachlimb of the fold by normal faulting would account for the differ-encein dip, and may also account for the convergence of the faultzones It i~ conceivable that such arching might have been

ARIZONA BUREAU OF MTNES

52

a

brought about by the intrusion of the Times porphyry which

may have been injected at a low horizon in the volcanic series,

and may rest on the old granitic rocks If the magma moved

up-ward at an angle in a northwesterly direction, it might readily

take the form of a laccolith, and such type of intrusion is known

to produce an arching of its cover Remnants of Alcyone trachyte

which rest on the Times porphyry are parts of such a cover, but

the base on which the porphyry rests was not seen There is,

therefore, no conclusive field evidence to show that the intrusion

is a laccolith

AGE, TYPE, AND DISPLACEMENT OF FAULTS

Among the earliest faults definitely recognized are the

frac-tures occupied by the rhyolite porphyry dikes These dikes show

a radical arrangement around three sides of the Times porphyry

and appear to be a direct result of the intrusion of this porphyry

Many of the dikes are offset by the mineral-bearing fractures

as is well shown in the northern part of the district where the

two nearly parallel dikes are cut by the Pasadena vein In somB

cases faulting prior to the formation of the veins fonowed these

dikes, and the vein occurs on one wall of the dike Examples of

this phenomenon occur in the southeast corner of Section 23, and

also at the east end of the Esperanza vein

Renewed movements on the faults after some of the

vein-filling had been deposited, and before the last stages of quartz

and calcite were introduced into the veins by the

mineral-bear-ing solutions, resulted in a crushmineral-bear-ing of the earlier, depos.it ofv~in

materials This period of faulting is important and WIll be

dIS-cussed more fully in connection with the ore deposits

Faulting later than ore deposition is well illustrated by the

Mallory fault which in its northern extension follows along a

rhyolite-porphyry dike (see Plate 1) It cuts across the Tom

R~edvein near the Big Jim shaft, follows the course of this vein

for a short distance, and then takes a rather sinuous course past

the Sunnyside shaft and up the cliff to the south Near the Big

Jim shaft, the Mallory fault is offset about 300 feet by the

Oat-man fault Some of the faults which cut the basalt flows may

represent a post-mineral movement along pre-existingfractur~s,

for none of such faults cutting basalt was found to carry

vem-filling

All of the faults described above appear to be of the normal

type; that is; the hanging wall has gone down with respect to ~he

footwall Some reverse faults occur, however, in the Katherme

55

THE OATMAN AND KATHERINE DISTRICTS

District At the Katherine Mine, the ore body is cut by a series

oflow~anglefaults which appear to have pushed the hanging wallsegment upward A longtiudinal section of the mine whichshows this feature will be found under a description of thi~

mine

The absence of good horizon markers makes it difficult to te~'mine th.e displacement of the individual faults Many of the

de-~me:vorkmgs are comparatively shallow, and only in the

produc-mg mmes are depths of a thousand feet or more attained Manyshafts have been put down to depths of 300 to 500 feet, but suchsha~tsare commonly in only one kind of rock and yield no infoI"

~atlOn on the amount of displacement Quite frequently, twokmds of rock, such as andesite and latite or andesite andtrachyte, are brought in contact by faulting and, in some suchinstances, it is possible to determine the min'imum vertical com-ponent of faulting On the Mallory fault, the vertical displace-ment of the Tom Reed vein between the Big Jim and Grey Eagle

is about 500 feet Very likely the displacement on similar tures, such as the Tom Reed or Gold Road is of about the same

1 shaft, it is,,~2ertainly500 feet and! may be eve~ more

: /\. ".":;;' Branchi:J;lg 6f the faults is a common feature in the OatmanDistrict Near the Red Lion shaft, the Telluride fault appears to

-be a ,:est branch of the Tom Reed fault, and a similarbra~!Ching

on th.lS fault occurs a short distance to the northwes,t of tli BenHarrIson shaft On the east branch of this fault, the ' nitedEastern ore body was formed Still farther northwest, theTom Reed fault again branches into two parts

OR,E DEPOSITS

DISTRIBUTION OF VEINS

The veins occupy fault fissures or fractures in the enclosingrocks; no exceptions were noted The distribution of the veins,therefOl:e, bears an intimate relation to the distribution of thefractures or faults which have been described in a preceding sec-tion of this report Certain features of the occurrence of thevein-filling in these fractures are important

ARIZONA BUREAU OF MINES

54

Fig lO.-The hanging wall portion of the Gold Dust vein, showing

stringers in the wall rock.

THE OATMAN AND KATHERINE DISTRICTS

STRUCTURE OF THE VEINS

The structure of the vein is sometimes quite simple and sists of a tabular body of quartz and calcite with well definedwalls Most of the deposits, however, are lodes whidh consist of

con-a lcon-arge number· of stringers or veins vcon-aricon-able in width con-and sepcon-ar-ated from each other by barren rock Where there has been nopost-mineral faulting, small ramifying stringers branch from themain vein into the wall rock Such side stringers arp, mineralogi-cally similar to the main vein from which they branch, and mayconsist of either quartz or calcite, or an intergrowth of both min-erals Frozen contacts are common, particularly in those veins

separ-on which there has been no post-mineral faulting Even in theveins showing' late faulting, one wall may be frozen to the coun-try rock

Some veins or lodes consist entirely of a great number of culating stringers which traverse the country rock This type

reti-of deposit is well shown in portions reti-of the Gold Dust vein in theOatman District and in the Frisco vein in the Katherine Dis-trict Compound veins, which consist of two or more veins ofsolid quartz; and calcite separated by country rock, are common

in both districts The intervening country rock is commonlytraversed by stringer veinlets, and, when these stringers aresufficiently abundant, the country rock which contains the vein-lets may constitute ore

ARIZONA BUREAU OF MINES

Fig 9 -View showing the structure of the Gold Road vein

vith nearly vertical stringers of quartz.

It will be well, perhaps, to state now that many of the faults

which have a length, as shown on the ~ap, ?f thous~nds.of feet

ot filled for their entire extent wIth vem matenals, on the

~~~t~ary,there are frequent interruptions inth~vein Inf~llow­

ing a vein along the strike from one prospect pIt to anot~el,the

vein-filling is often found to diminish, and, in places, entIrely to

disappear' but the fault continues as a crushed zo~e Fart~er

along thi~ same fracture, the vein-filling will agam come l~

During the field mapping, an effort was made to show the w~dt

nd extent of the vein-filling along the fault, but, as ~ strong

~ein may end in a few small stringe:'s, it was foun.~ dl~cult to

show these features on a map An mS.lgm~cant stn~geI at the

surface has been found to lead to a solId vem of quaItz a~d

cal-cite three feet thick at a depth of only thirty feet on the dl~), and

similar variations in width may be observed along the stnke of

the vein

56

The ribbon structure, so common in the Mother Lode of

Cali-fornia, was not seen in these districts; but a paralled sheeting,

simulating such ribbon structure, occurs in the ore at the

Kath-erine Mine,' and to a lesser extent in the Gold Road vein

Fragments of wall rock are frequently enclosed in the veins,

and such fragments are in most cases quite angular in outline

Many of these fragments are surrounded by concentric layers

of quartz Where the calcite surrounds rock fragments, the

banded structure is less evident, but, if the calcite is fine grained,

banding may occur Many of the small stringers in the walls

occupy joints and irregular fractures, and these veinlets appear

to have filled open fissures rather than to have replaced the wall

rock, although it is possible there may have been some

metaso-matic replacement, but the extent of this replacement cannot be

determined During the process of ore deposition, open fissures

must have existed; otherwise the thin plates of calcite could not

have formed as they did

MINERALOGY OF THill ORES

The mineral composition of the veins is comparatively simple

and consists essentially of quartz and calcite with smaller

amounts of adularia, fluorite, and gold During the process of

oxidation, but few additional minerals were formed, and, among

them, gypsum, hematite, and pyrolusitel are the most common

Sulphides are rarely found in the veins,but are commonly

en-countered in the walls of the veins

always alloyed with more or less silver In most of the ore

hav-ing a value of less than $20 per ton, &ilver exceeds gold by weight,

but, in such ore, the precious metals are so finely divided that

they are rarely recovered by panning High-grade ores

fre-quently show free gold When such gold is primary in origin, it

occurs as aggregates of small, hackly grains, as slender curved

wires resembling trichites in volcanic glasses, or as thin plates

between grains of quartz Coarse gold is rarely found Such

gold is of a pale, brassy yellow color and contains approximately

20 percent by weight of silver Gold, believed to be of supergene

origin, occurs as loose flakes and wires in vugs with the oxides

of iron and manganese This secondary gold is almost always in

larger particles than the primary gold Its color is a deep, brassy

yellow and it may contain as much as 10 percent by weight of

silver, or much less

Visible particles of primary gold in the richer ore is most

com-monly found embedded in quartz grains, less commonly in

pIes of c~lcite which are heaVily s~:iln:dalt~ou~h many

sam-gan~s~ oXIdes carry gold wIth Iron and VIsIble gold in quartz, particul 1'1

man-IS usually confined to layers 1 a fhIllthe hIgher grades of orethickness When examined m·ess a~ one-tenth of an inch i~

show crystal outlines T''l IC:do~coPlCallY, SOme isolated grains

Pal IC es of gold are embedd d" IC carry VIsible

'.~ III adularia is rather uncom speCImen from the United E t mon, but was observed in asome rich ore from the Gold~s ~~?re body A thin section ofgr?wth of quartz grains ando~ t· Ille

f showed a parallel

A speCImen of fluorite from t ~merals

rather stout wires and hea 1the Moss vem contained some

of fluorite Some of the fl:Y'~a /s of gold between the grainstains visible gold Oll e rom the Hardy vein also con-

gold, and, in sorde ores th::.t e ' al;ay~ occurs alloyed withnever in value Silver Creek ~:~l p.~e ommates by weight, butthe ores from mines along this st~~I s name fron; the fact thatThe general impression amon l' am car~'Y conSIderable silver

tain the silver sulphide arge~lttoS1e~t~~ISt~at these ores served in any of the sp'ecI'm e, u IS mmeral was not ob-

pu verent manganese oxide 1 't IS POSSI Ie the

for a SlIver mineral.· Accordin, pyIO USI e may have bto R' H . . een mIS aken tcopper-stained quartz from oneg f th' 1 DImmIck, an assay ofedne Mine gave a high ret ,0 • e ower levels of the Kath-some chalcocite and may al~r~III SlIver: The sample contained'All persons questioned agr~e t~ve car~Ie~some argentite

these gold ores and non at hOln SlIver does not OCcur inthat this minoi'~lmay bee was sete~ by the writer :rt is possible

dlzed ores and yet not be visible A uan : Ies m the

OXI-ed at the Arizona Bureau f M·' speCImen of WIre SlIver the San Francisco Mining ~i t~~~s;;ras said to have come fromknown s llC, ut the exact locality is un-

chalcocite at the Gold 0 ' un a Ittle chalcopyrIte andchalcopyrite in ore at Bi~eJ~~n'T~nd t~e ~riterfound specks ofhas given rise to copper-stained e,~xldatlOn of t~ese sulphidesbut chrysocolla is common in suc~ual z~ No ~~lachltewas found,quartz occurs to.a limited ext t qtUtah1tz SImIl~rcopper-stained

en a e Katherme Mine

Op, cit p 33.

ARIZONA BUREAU OF MINES

58

Lead Minerals: A pulverent, bright red mineral was found in

cavities in ore from the Big Jim Mine, by J.W Bradley At first,

it was thought this red powder might be cinnabar, but blowpipe

tests indicate lead rather than mercury Itis possible this

min-eral is the red oxide of lead, minium Several specimens

col-lected on the dumps at the Big Jim and also at the Aztec shaft

contained a thin film of a bright yellow mineral Blowpipe tests

show it to contain lead and molybdenum, and it is probably

wulfenite Similar material was collected from the Pioneer vein

found in the veins although it is quite common in the wall rock

adjoining the veins In a few instances, it was observed

embed-ded in quartz, and a specimen of quartz from the United

American Mine contained small cubes of this mineral

Irregu-lar grains and crystals of pyrite were also identified in a

speci-men from the Moss vein A sample of the altered wall rock

which contains pyrite, from the United American Mine, was

crushed and the pyrite was concentrated by panning These

con-centrateswere then examined microscopically, but no gold was

seen An assay of this pyrite-concentrate gave only a trace of

gold and silver

Marcasite was found with pyrite in quartz at the Moss vein

The mineral occurs as groupS of thin plates which diverge

slight-ly at each end It could not be separated readislight-ly from the pyrite

for assay, and, consequently, it is not known whether or not the

mineral is gold-bearing

com-mon in, the oxidized ores of both districts, and have been

de-rived from the oxidation of pyrite and perhaps, also, from the

breaking down of ferromagnesian silicates in the wall rocks

Porous quartz which contains an abundance of hematite

fre-quently also carries small flakes and wires of free gold Such

gold is of a deep, brassy color and is believed to be supergene in

origin

man-2;anese is rather widespread in distribution It appears to be

particularly common,though never abundant, in the western

part of the Oatman District where it is associated with ores

con-taining fluorite Chemical tests show some of the calcite to

carry manganese, and it was probably from this source that the

manganese oxide was derived

consti-tuent of the veins and shows considerable diversity in both

tex-60 ARIZONA BUREAU OF l]1lINES

THE OATMAN AND KATHERINE DISTRICTS 61

ture and color It occurs in sever 1 ated with calcite and in a generatIons, always associ-The first depo~itio~of sqoUmetSP~cImens,with adularia

gramed, colorless variety in cryst I t ns was a length Some quartz is mostly :h\up 0 an mch or more inwhich possess an amethystine tint I e, but shows some bandscases, however, this early quart cros.smg the crystals In mostterlocking grains instead of crys~:l~~slStsof an aggregate of in-Yellow quartz is most common' th

coarse-has a decidedly greasy lust " m e h~gher grade ores andexamination of sections ofe~h:nsowe speCImens A microscopicgrains are filled with an ' IS ye ow quartz shows that thebut these tiny scales area:gI egate of mm~teplumose inclusions;fusion of this yellow tOO small for optIcal determination A

it is possible that theer;~~o~gare ~ d~fimte reaction for iron, andBanded quartz chalce C? or IS ue to some iron silicate.Road vein and also at thdoenGIcoIldn toexture: is abundant at the Goldh

w Ite to cream, or even pinki h · qual' z may be

Much of it is white to grayish~ tm a:undance m the veins

in texture, forming large rh mbCOo\an rather coarse grainedSome varieties of the calcitehom s ,WI h cur~ed cleavage faces.ular to the base and well ave gIown as thm plates perpendic-the rhombohed;al f -developed crystals of this mineral showChemical tests g~~:saaI~~~~~ ~~e~dges ~f the cry~tals.

iron, and a specimen from th p' agn:sIa, sometImes a little

a test for manganese e lOneer vem, pinkish in color, gave

d

' u ana IS a common constituent of th h' hgra e Olej and m such ' ' t ' " e Ig eryellow quartz.' Thed ~I:: I IS mvarIably associated with thetween layers of qu:rt~ aI~a tus~allY occurs as white bands be-adularia and grains ofq~artU , m :ome specimens, plates of

ly found as an a Te z a;- e I? ergrown Gold is plates of g lel gg f gate~fgrams~n such intergrowths, and thin

frequent-o were ound m adularIa .Bands of pure adularia v r ' dth

an inch up to nearly two in~~:n ~~ from a small fraction ofbands show the crystals t b' ~avagefaces on these broad

~arge:'crystals have well-de~elo;edq~~~:ni~~f~e ~reqduetnhtlY,theIdentIfied are the base and l' ace~,an e forms

a microscopic constituent oc/~~~o:,:Ss' Ad~larla alsoo~cursascrystals surrounded by quartz as ISO ated grams and

b An analysis of the adularia from the Oatman District d

p;"~~t~~e~'s~~~a~::~u;::~ Y.niversity of Arizona, Yielde::~h: